A browse will show you there are a number of threads on this area of the forum on the subject of Trangia's.
In summary:
Get gas, but take the meths burner with you
The screw on gas bottles used in most of Europe are not easy to get in France, but can be found in hardware shops and proper cook shops as paint strippers and brulee burners use them. Also you may find them in some campsite shops where they get in a lot of English/Dutch backpackers or cycle tourists
There is a converter that can be got that converts pierced gas into screw gas.
Get the full Trangia 25K teflon (the bigger one, with the kettle and the non stick surface) You can always leave the bits you don't need out for a trip, but when weight does not matter it's good to have all the bits.
'Optional' Trangia items that are also worth getting are:
The plastic strainer (I don't know why it's optional, as it's not)
The bag to put the entire stove in
A second gripper (one is not enough)
A Tupperware circular butter dish that fits inside the kettle. This is where you keep the meths burner. (Again, not really an 'optional' item, as it means your food does not taste of meths, or your clothes smell of meths)
The 1 liter Trangia meths bottle - much easier to pour from, so saves meths.
It's also worth going into a proper kitchen/cooking shop as I also have as part of my kit:
A paring knife (about a 3" blade, with a sheath)
A nutmeg grater (it's a micro cheese grater)
Salt and pepper mills (About 1" high)
Several very small containers for herbs and spices
A Union Jack tea towel (doubles up for peak bagging)
I also divide up all the pots and pans etc with quarter sections of a J-Cloth, stops things rattling and can be used for washing up.